The objective of this project is to study the microbial flora of the cancer patient; i.e., to determine acquisition, colonization and subsequent infection. Routine surveillance cultures of patients determine which organsms are acquired. New and unusual organisms are extensively studied. Proteus spp. and Serratia are subspeciated to specifically identify strains. Acquired organisms more frequently cause infection than the original patient flora. Patients placed on the combined antibiotic therapy protocol are monitored for infectious organisms. A comparison of the susceptibilities of P. aeruginosa to four antibiotics was done due to increased resistance to antibiotics in routine use. The results of this comparison demonstrated differences important for patient therapy. A comparison of positive skin cultures taken from patients in the new BCRC setting with those taken in the previous BCRC setting at the PHS Hospital has led to revised procedures of skin care.